1. Field of the Invention
The present invention relates to an ultrasonic motor.
2. Description of the Related Art
Currently, ultrasonic motors with a reduced size, a higher torque, a longer stroke, and a higher resolution as compared with those of an electromagnetic motor are widely used.
Presently, the ultrasonic motor is a motor for driving a member to be driven by frictional force generated between an ultrasonic transducer and the member to be driven by pressing the ultrasonic transducer on the member to be driven. As a pressing mechanism for pressing the ultrasonic transducer on the member to be driven, such a pressing mechanism as shown in FIG. 12 has been disclosed, for example, in JP-A-10-327589.
That is, in JP-A-10-327589, the pressing mechanism is provided with a transducer 114, protrusions 113 fixed on a lower portion of the transducer 114, a rail 118 serving as a movable member abutting on the protrusions 113, rotary members 112 contacting with a lower face of the rail 118 and guiding the rail 118, a spring member 117 caused to abut on an upper face of the transducer 114, a rubber sheet 115 disposed between the spring member 117 and the transducer 114, a columnar retainer 121 extending through the spring member 117 and the rubber sheet 115 to be fixed to the transducer 114, and a fixing member 119 pressing the spring member 117.
More specifically, the spring member 117 is provided with a flat face portion 117a contacting with the rubber sheet 115 and flat face portions 117b and 117c formed to extend from both ends of the flat face portion 117a symmetrically regarding the flat face portion 117a. Distal end portions of the flat face portion 117b and the flat face portion 117c are pressed down by the fixing member 119 so that portions of the spring member 117 in the vicinities of boundary lines between the flat face portion 117a, and the flat face portions 117b and 117c are deformed. Thereby, the flat face portion 117a is pressed downwardly (in a direction of the transducer 114).
In the pressing mechanism disclosed in JP-A-10-327589, a pressing force for pressing the transducer 114 (the protrusions 113) on the rail 118, which is the member to be driven, is generated according to such a structure as described above.
A rectangular through-hole portion (not shown) is provided in the flat face portion 117a of the spring member 117. Further, a similar rectangular through-hole portion (not shown) is provided in the rubber sheet 115 provided so as to be sandwiched between the spring member 117 and the transducer 114. The columnar retainer 121 extends through the rectangular through-holes (not shown) provided on both the spring member 117 and the rubber sheet 115 to be fixed to the transducer 114.
The columnar retainer 121 is provided such that side face portions thereof are surrounded by sections of the through-hole portions (not shown) of the spring member 117 and the rubber sheet 115. The position of the transducer 114 within a plane thereof contacting with the rubber sheet 115 is restricted by the structure.